Diffusion Tensor Imaging of Knee Cartilage for Detection of Early Osteoarthritis and Prediction of Radiographic Progression

BACKGROUND: The progression of early osteoarthritis (OA) is difficult to predict radiographically. T2 mapping provides information about cartilage degeneration, but its sensitivity to early matrix injury is limited. Diffusion tensor imaging (DTI) may detect cartilage microstructural abnormalities beyond T2 mapping. PURPOSE: To test whether baseline cartilage DTI metrics are associated with early knee OA and 3-year radiographic progression, and to compare their performance with T2 mapping and baseline Whole-Organ Magnetic Resonance Imaging Score (WORMS). STUDY TYPE: Prospective longitudinal cohort. POPULATION: Seventy-one participants (40 female, 31 male): 60 with unilateral symptomatic OA (one knee Kellgren-Lawrence [KL] ≥ 2, contralateral KL = 1) and 11 asymptomatic controls; 40 OA participants had 3-year follow-up radiographs. FIELD STRENGTH/SEQUENCE: 3T, radial spin-echo diffusion (RAISED) DTI and multi-echo spin-echo T2 mapping. ASSESSMENT: KL grade, joint space width, baseline WORMS, and cartilage segmentations were obtained. Mean diffusivity (MD), fractional anisotropy, axial diffusivity, radial diffusivity (RD), and T2 were calculated in six cartilage regions. Progression was defined as joint space narrowing (JSN) > 0.7 mm or any KL grade increase. STATISTICAL TESTS: ANCOVA adjusted for age, sex, and body mass index. Discrimination was assessed with the area under the receiver operating characteristic curve (AUC); predictive models were evaluated using cross-validated AUC. A two-sided p < 0.05 was considered statistically significant. RESULTS: Baseline medial femoral condyle (MFC) MD distinguished KL = 0 from KL ≥ 1 knees (AUC 0.90), whereas a T2-based model showed lower discrimination (AUC 0.55). Among KL = 1 knees, 30% showed JSN progression and 28% KL progression. Baseline MFC MD and RD were higher in progressors, and adding MFC MD improved prediction of radiographic progression (AUC 0.80 for JSN and 0.71 for KL). DATA CONCLUSION: Baseline cartilage DTI, particularly MFC MD, showed stronger associations with early knee OA and radiographic progression than T2 mapping. EVIDENCE LEVEL: 2. TECHNICAL EFFICACY: Stage 3.